CVE-2009-3721Public exploit

Arbitrary code execution via oversized attachment filename

Published May 26, 2021 · Updated Aug 7, 2024

Stack-based buffer overflow in ytnef 2.8 allows attackers to execute arbitrary code by decoding a TNEF attachment with an oversized filename. ProcessTNEF uses sprintf to copy the attacker-controlled filename into a fixed 256-byte stack buffer without enforcing its capacity. The crafted file must be decoded by a target user; successful exploitation runs code with that user's privileges, while failed attempts can crash the process.

CVSS severity7.8
High
EPSS probability1.61%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stack-based buffer overflow in ytnef 2.8 allows attackers to execute arbitrary code by decoding a TNEF attachment with an oversized filename. ProcessTNEF uses sprintf to copy the attacker-controlled filename into a fixed 256-byte stack buffer without enforcing its capacity. The crafted file must be decoded by a target user; successful exploitation runs code with that user's privileges, while failed attempts can crash the process.

The record

CVE
CVE-2009-3721
Published
May 26, 2021
Updated
Aug 7, 2024
Vendor
Yeraze
Product
ytnef
Classifications
CWE-22, T1203
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 26, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 7, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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  1. Affected versionversion=ytnef 2.8

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Yeraze · ytnefversion=ytnef 2.8

Published CVSS scores

7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
7.8UbuntuCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
6.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:P

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
T1203Exploitation for Client Execution

Public exploit references

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Technologies

Your stack

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Your stack

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